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Crankshaft shimming #791297 11/25/19 9:39 pm
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CarpeDiem Offline OP
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Hi, I was wondering if when you are checking crankshaft endplay if you make allowance for the crankcase sealant ? Since you might need to add shims as required you wouldn't want to apply crankcase sealant until shims installed. Also is the bearing on the primary side loctited into the case if loose or is it installed on the crankshaft. The questions are in regard to 1965 BSA A65 lightning. Thanks Rebuild Rookie.

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Re: Crankshaft shimming [Re: CarpeDiem] #791310 11/26/19 12:21 am
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For the difference the sealant will make, no.


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Re: Crankshaft shimming [Re: CarpeDiem] #791319 11/26/19 1:47 am
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In a 1965, the crank would originally have had a ball bearing, which would be pressed into the case on the primary side. It should not be loose in the case or require loctite.

Re: Crankshaft shimming [Re: CarpeDiem] #791353 11/26/19 10:48 am
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As MarcB stated, a 1965 model would have had a bearing on the drive side

You would not be "shimming" the crank should you be running a ball bearing

The only shimming you would do is to ensure your connecting rods are in the center of the liners

Get a spacer, washer and a rotor nut and tighten the drive side crank-end so the crank "shifts" to the drive side

From there, you can use some telescopic gauges and check the rods when you slip the barrel on

Also, your ball bearing inner race should be a tapping fit on the crank journal, if it is not, you can add some loctitie, but that will not cause end-float issues as your assembly will be fixed on the drive side

Good luck!


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Re: Crankshaft shimming [Re: C.B.S] #791354 11/26/19 11:10 am
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Originally Posted by C.B.S
As MarcB stated, a 1965 model would have had a bearing on the drive side

You would not be "shimming" the crank should you be running a ball bearing

The only shimming you would do is to ensure your connecting rods are in the center of the liners

Get a spacer, washer and a rotor nut and tighten the drive side crank-end so the crank "shifts" to the drive side

From there, you can use some telescopic gauges and check the rods when you slip the barrel on

Also, your ball bearing inner race should be a tapping fit on the crank journal, if it is not, you can add some loctitie, but that will not cause end-float issues as your assembly will be fixed on the drive side

Good luck!


Not true, the oil pump will pull the crank towards the timing side, this will in turn actually pull the ball bearing away from its housing so the shimming of the crank is just as crucial as on a roller bearing crank. The crank will shift to the drive side when tightened at build stage but will shift after a couple of thousand miles.

Also the use of bearing fit should be used in the worst possible situations. Even then I’ve found a sloppy housing then be too tight for the bearing once bearing fit is used. Standard procedure is to repair the housing.

Simply put follow MarcB’s advice.


beerchug
Re: Crankshaft shimming [Re: CarpeDiem] #791386 11/26/19 4:14 pm
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Since I have taken a liking to the early unit twins.....

Marc & Allan are correct. You do have to shim the ball bearing cranks, you actually set running clearance between the crank and shoulder of the timing side bearing housing. .0015" - .003", sealant is not an issue.

Note, ball bearing engines, you check "end play" by checking the crank without the alternator rotor (or equivalent spacer) and nut not installed.

Roller bearing engine needs everything installed and tight.

You also need to shim the primary chain to keep from loading the crank. There are shims for that as well. A straight edge is as complex as you need to be on checking primary chain alignment.

The rods journals being centered are a myth. They are what they are due to the components used and BSA machining. The journals will be "reasonably"close to center with all correct components installed.


Never underestimate the human ability to elevate stupid to a whole new level!.
Re: Crankshaft shimming [Re: CarpeDiem] #791413 11/26/19 10:31 pm
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The rods journals being centered are a myth. They are what they are due to the components used and BSA machining. The journals will be "reasonably"close to center with all correct components installed.


In your opinion only.
To get the best from the engine in terms of longevity and vibration etc. Centre them. Each to his own eh?

Re: Crankshaft shimming [Re: CarpeDiem] #791414 11/26/19 10:44 pm
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Some points here


- loctitie, referring to the crank journal NOT the housing

- Connecting rods being centered in the bore is a good thing to check, especially when cranks and cases have been changed - each his own



Last edited by C.B.S; 11/26/19 10:49 pm.

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Re: Crankshaft shimming [Re: CarpeDiem] #791421 11/26/19 11:44 pm
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Makes no odds where you fit the locktite. It will still add a small amount of bearing crush and cause the ball race to run rough. It also should be a good fit on the crank and more often than not the case will wear before the crank. In many cases the bearing will actually spread on the crank journal rather than wear on the crank.

Back to the shimming, if you shim a crank to perfect centre then you have never tore the motor down afterwards least on the primary side and seen the bearing drift out of its housing. The only thing that will stop that happening is shimming the crank or an out rigger bearing outboard the primary drive/alternator.

As you say each to their own but the guys at BSA weren’t stupid, vehicles may have come on leaps and bounds in the last 50+ years but they didn’t add things to the WSM just because it seemed a good idea at the time. They made the best of what was available and understood very well what they were working with.


beerchug
Re: Crankshaft shimming [Re: CarpeDiem] #791431 11/27/19 12:15 am
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Understood, but there are many ways to fix a common problem

You can weld the crank, hard chrome it or loctite it

Depends on the application and what that individual person feels should be done

You have your opinion on this, as do I


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Re: Crankshaft shimming [Re: Allan Gill] #791433 11/27/19 12:49 am
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Originally Posted by Allan Gill
Makes no odds where you fit the locktite. It will still add a small amount of bearing crush and cause the ball race to run rough. It also should be a good fit on the crank and more often than not the case will wear before the crank. In many cases the bearing will actually spread on the crank journal rather than wear on the crank.

Back to the shimming, if you shim a crank to perfect centre then you have never tore the motor down afterwards least on the primary side and seen the bearing drift out of its housing. The only thing that will stop that happening is shimming the crank or an out rigger bearing outboard the primary drive/alternator.

As you say each to their own but the guys at BSA weren’t stupid, vehicles may have come on leaps and bounds in the last 50+ years but they didn’t add things to the WSM just because it seemed a good idea at the time. They made the best of what was available and understood very well what they were working with.



Don't quite understand what you are saying regarding centreing the crank.
This procedure normally involves making a bronze washer to suit the timing side as well as shimming or making a spacer for the drive side.
As you said before the natural thrust of these motors is toward the timing side due to the oil pump, this tends to pull the bearing out of it's
housing with a ball type if the movement is not restricted. With the roller this is not a problem unless using a double flanged one.
If you have to use loctite 638/641 etc on the drive side housing, you can normally get away with it if you use a c3 fit bearing. Stopping the
bearing moving by applying the previous method will help prevent the housing growing anyway.
Everyone has their own methodology with these things, normally if you haven't encountered any problems with a method, you don't change it.
It's a 'if it ain't broke........thing. Most of my experience on these was racing them, so i got plenty of problems........................................

Re: Crankshaft shimming [Re: CarpeDiem] #791435 11/27/19 1:28 am
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I was probably straying from my original point Nick, it’s quite late here and I aught to try and get some sleep. What I should say is there is nothing wrong in centring the crank providing you correctly shim (with shims and or a form of bronze thrust face on the timing side) to give the correct amount of end float.

centring alone without taking into account the end float is foolish. As unless you create a bearing retainer plate (which there would probably be no room for) the bearing will walk (or use an outrigger).

Adding anything to the crank is irrelevant as far as bearing walk is concerned Between the crank and the inner bearing race, doing anything to this surface is just kidding yourself. Once the end nut is bolted up there should be no lateral movement. If there is some clearance between the crank and the bearing then I have seen the ID of the bearing grow and become a slop fit. The first note I had of this was with Increased vibration. never found that on a ball bearing but have with the same crank when a roller was fitted. There was never any slack in the end nut. The bearing became a throw on fit and the replacement bearing was tight to the crank.

Put another way if you have to add locktite or hard chrome or what ever to that crank journal then you really aught to be looking at changing the DS bearing or at least checking it against a new one.

( I think we’re also moving off topic for the sake of a pissing contest. )


beerchug
Re: Crankshaft shimming [Re: CarpeDiem] #791447 11/27/19 5:50 am
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Ahh, now i understand what you mean Alan. No pissing contest intended here.

Nick

Re: Crankshaft shimming [Re: NickL] #791453 11/27/19 7:57 am
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Originally Posted by NickL
Ahh, now i understand what you mean Alan. No pissing contest intended here.

Nick


I didn’t mean you Nick lol. I hold your knowledge on the subject in high regard.


beerchug
Re: Crankshaft shimming [Re: CarpeDiem] #791483 11/27/19 9:49 pm
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Hi, I am processing all the inputs, Thanks to everyone, I am sure your expertise will be tapped again. Rookie Rebuilder.

Re: Crankshaft shimming [Re: CarpeDiem] #791500 11/27/19 11:40 pm
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Hi, does the retaining cup on the primary side(between bearing and crank) get place curved edge facing crank or the other way around so has flat edge for shimming? not clear in manual. Thanks Rookie Rebuilder.

Re: Crankshaft shimming [Re: CarpeDiem] #791501 11/27/19 11:53 pm
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The shims sit in the cupped side, this then sits on the bearing inner flange.
If the cup does not sit on the flange it may be an early type cup on a later bearing type.
They changed the bearing in the late 60's and the inner diameter was different.
It's a nuisance i know, but around that time a few bearing manufacturers were amalgamating.

Re: Crankshaft shimming [Re: CarpeDiem] #791504 11/28/19 12:12 am
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Doesn’t centering the crank have to take into account end float, within a certain number of thou, by definition?

Restricting end float will surely limit how much a ball main on the drive side can “walk” toward the timing side.

Is this “walking” a proven fact? Only ask because it is a debated phenomenon in Triumph engines as well, and I’m far from convinced.

Re: Crankshaft shimming [Re: koan58] #791507 11/28/19 12:43 am
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Originally Posted by koan58
Doesn’t centering the crank have to take into account end float, within a certain number of thou, by definition?

Restricting end float will surely limit how much a ball main on the drive side can “walk” toward the timing side.

Is this “walking” a proven fact? Only ask because it is a debated phenomenon in Triumph engines as well, and I’m far from convinced.


The beezer has an oil pump driven from the crank, this creates a thrust toward the timing side.
The early crank used a ball race on the drive side to retain the crank, when the cases heat up the
thrust tends to pull the bearing from it's housing as there is no thrust washer on the timing side.
I have seen this on several occasions. The matter is enhanced if the later crank is fitted with a ball race.
I am not saying centreing and shimming/spacing is the only way to go, but from experience it is a definite
improvement. As i said before, if you haven't had the problem you wouldn't see the need.
Getting the crank central is always a good idea anyway, if only for longevity.
When i raced a pre-unit morgo trumpet we used 2 rollers so shimming was required anyway.
I just feel that relying on interference fit bearings to retain the position of the crank when it can move
2 or 3mm without spacers/shims is not such a good idea.
It's only my take on it, it's not the law.

Re: Crankshaft shimming [Re: CarpeDiem] #791511 11/28/19 2:01 am
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Thanks Nick, makes perfect sense. You might have noticed I’m not a BSA man.
I am surprised there isn’t a thrust washer on the timing side, considering the bias of the oil pump, and I’d have thought that centering the crank would quite possibly involve shims to both sides (limiting end float at the same time surely?).

The maximum the drive side bearing could “walk” out from its housing would surely be the few thou end float that has been set (hopefully not 2-3mm).

If that truly happened, the next time you measure the end float it would be zero, or much less than originally set, unless you imagine the bearing moves back into its housing as it cools.

I recall similar interesting conundrums regarding pre-unit Triumphs with 2 ball-bearing mains – what gives during temperature expansion changes?

Re: Crankshaft shimming [Re: CarpeDiem] #791512 11/28/19 2:42 am
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The post '66 ones went to roller drive side and had a thrust washer on the timing side.
The ball race (earlier ones) did not. The crank was also wider across the webs.
It relied on the fit of the drive side race.
The available movement varies (without shims/spacers) enormously. If it's only a few thou then, no problem.
As with all production stuff back then, tolerances were variable, and the assembly relied on a bloke/blokes
on piece work doing the job. The cases were marked for shimming sizes. If he found that a few were tight,
the next 20 he did would probably be loose as he didn't want to do the job more than once.
Same score with gearboxes, i don't think i've ever seen a standard a65 gearbox layshaft set up properly
on an original bike. If they were tight, the box had to come out again............so......
50's and 60's production lines for workhorse motorbikes and cars were like that, like it or not. These were not Bentleys.

You are also relying on the fact that the engine is all as it came from the factory.
If a late crank is fitted to an early motor it will have a lot of movement available.

The cases grow so much as they heat up, end float is increased anyway. I hear a few people say the
crank expands at a higher rate from cold initially but a couple of thou maximum is all i ever allow.
Normally setup the crank to just binding, then some sealant on the cases gives the required end float.
With a warm motor it'll be 5+ at least.

Re: Crankshaft shimming [Re: CarpeDiem] #791515 11/28/19 2:54 am
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Cheers Nick, makes sense.

" I hear a few people say the
crank expands at a higher rate from cold initially"

I don't see how that could possibly be true, considering the heat pathways from the top end and expansion coeffs of steel vs alloy.

Re: Crankshaft shimming [Re: CarpeDiem] #791517 11/28/19 3:03 am
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Well,,,,,,,,, that's my take on it but a few blokes here say they have pushed bearings through the primary case
due to insufficient end float setup. They say the immediate heat generated by the engine makes the crank
grow faster than the cases from cold. I've never experienced it but that's what they say. Maybe they assembled
the engine in very cold weather?

Re: Crankshaft shimming [Re: koan58] #791530 11/28/19 9:48 am
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Originally Posted by koan58
Doesn’t centering the crank have to take into account end float, within a certain number of thou, by definition?

Restricting end float will surely limit how much a ball main on the drive side can “walk” toward the timing side.

Is this “walking” a proven fact? Only ask because it is a debated phenomenon in Triumph engines as well, and I’m far from convinced.



The crank big end journals have a certain amount of play which the rods can run, there is also a mahoosive gap between the rod and the piston gudgeon pin boss, hence why you shouldn't have to worry too much about crank centering.

The crank walk is prooven enough. My own setup has a needle roller on the timing side, I use an outrigger bearing on the drive side to locate the endfloat. Following some not so good advice about the ball bearing not needing the outrigger (in my situation) as it would keep the crank located on one side, this I did. It meant I didnt have to space my primary case out, it also meant it would be easy to strobe time my bike.

After about a thousand miles I removed the primary cover to change a sprocket or something (can't remember what reason now) and found the front pully flush against the crank case, for the short time it had been doing this it has started to mill away against the crank case. Had I still been using a drive chain setup then the damage would have been much worse. The outrigger went back on!

Its worth noting that the bearing was a good and propper fit in the case, not a push in fit by any means.

My instance was more noticed becasue of the modifications to the TS giving much more end float than If I had a thrust washer fitted for example, If you imagine the thicness of a thrust washer then this is how much it would have walked by. If you have only 1 thou or 2 endfloat when cold then it is probably just enough to allow the crank to be pulled over to the thrust face on the TS bearing without having enough space to allow tollerence within the bearing but not enough to pull it off its seat... Im speculating, Its a good question which to that bit I don't know the answer.


beerchug
Re: Crankshaft shimming [Re: koan58] #791531 11/28/19 10:12 am
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Originally Posted by koan58
Cheers Nick, makes sense.

" I hear a few people say the
crank expands at a higher rate from cold initially"

I don't see how that could possibly be true, considering the heat pathways from the top end and expansion coeffs of steel vs alloy.



From a previous experience with the same motor, I was having bearing cages crush, despite there being enough clearance to clear the crank, there was insufficient clearance when hot, power was being sapped and the needle roller was being crushed down onto the bearing cage. (creating more clearance was the mechanical change was made, this was before fitting the ball bearing DS bearing)

An example of heat coeff for steel vs alloy can be seeing if you drop a crank case in a warm heat soaked over vs putting in an oven then turning it on. If the oven is heat soaked the aluminium should expand more rapidly than the steel (bearing) and the bearing will drop out. Put them both in a cold oven and turn the heat on and they will both expand at the same rate, you stand as much chance the bearing dropping out then as you do with the cases at room temperature. The crank and cases will both heat at a similar rate.


Originally Posted by NickL


The ball race (earlier ones) did not. The crank was also wider across the webs.
It relied on the fit of the drive side race.


Are you sure Nick? the early cases were not machined as deeply if at all on the drive side Link thanks to CBS


beerchug
Re: Crankshaft shimming [Re: CarpeDiem] #791538 11/28/19 11:43 am
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The cranks are different widths definitely, as for the machining you've got me thinking now maybe the later ones are wider.....
but either way they need checking when putting the old crates together. Note that the flange on the timing side bearing is
thicker on the early type as well. Many of the ones i've worked on have been put together with mismatched odds and sods.
If you go through the exercise of centreing the crank etc it all comes to light and can be corrected with spacers/shimming.
Allowing any crank to be fitted in any set of cases with any bearing type. Blimey, i never expected the Spanish Inquisition................................
https://www.youtube.com/watch?v=HqF_nPbX_Ow


The coefficient of expansion of casting alley vs chrome-steel is at least 1.8-1 so the bearing will expand far less at 100 deg
when both materials are heat soaked, the case, as it is a larger mass will take a little longer to get there.
https://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html

Re: Crankshaft shimming [Re: Allan Gill] #791543 11/28/19 2:03 pm
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""From a previous experience with the same motor, I was having bearing cages crush, despite there being enough clearance to clear the crank, there was insufficient clearance when hot, power was being sapped and the needle roller was being crushed down onto the bearing cage. (creating more clearance was the mechanical change was made, this was before fitting the ball bearing DS bearing)

An example of heat coeff for steel vs alloy can be seeing if you drop a crank case in a warm heat soaked over vs putting in an oven then turning it on. If the oven is heat soaked the aluminium should expand more rapidly than the steel (bearing) and the bearing will drop out. Put them both in a cold oven and turn the heat on and they will both expand at the same rate, you stand as much chance the bearing dropping out then as you do with the cases at room temperature. The crank and cases will both heat at a similar rate.""



Mr.Gill All of the engineers I know will call this nonsense..


Arnstein

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Re: Crankshaft shimming [Re: CarpeDiem] #791544 11/28/19 3:17 pm
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Which bit, you've selected a large piece so please elaborate?

If your referring to the cases in the oven then try it!!!

If your referring to my example then please see the thread I did at the time. Lightning resto .
a small epset below:

Originally Posted by Allan Gill

I think when I had this apart last time I must have decided I didn't want to do it again. As it took a good bit of effort separating some of the parts. The barrels were well glued to the crank case.

I eventually got the cases separated the timing side was stuck within the needle rollers and whilst they rotated around its centre they would not leave the crank. So enlisting a rubber (peg) mallet, and drifting against the crank case I managed to seperate the two.

Sure enough the setup had crushed, despite it having free movement at the initial build stage. But instead of cracking the bearing outer cage, it crushed it, forcing the needle rollers to a taper and damaging the surface on the sleeve. It had also worn a recess into the crank web in the process.

[Linked Image from i1182.photobucket.com]

[Linked Image from i1182.photobucket.com]

Luckily I have another full width replacement sleeve.

The new bearing is much narrower, and I have retaining ring to take up the additional distance.
The new bearing is needle only. And does not incorporate the ball race which controls end float. Which is not required because of the out rigger plate I have on the drive side.

[Linked Image from i1182.photobucket.com]

I milled the raised part which would normally locate the thrust washer (a little crude but it does the job)

[Linked Image from i1182.photobucket.com]

fitted the new bearing

[Linked Image from i1182.photobucket.com]

and fitted the bronze ring, which may not be required

[Linked Image from i1182.photobucket.com]


I hope to find that this is where I have been loosing HP and top speed.

the cam bushings in the inner timing case will have to be reamed out to accept the 0.878" diameter (which must have escaped QC on its day of manufacture) standard being 0.874" so I now need to come across a ball bearing to fit the DS case cam bush and an adjustable reamer.

I am going to measure the original 68 crank and the OIF crank (now in use) and note the differences


beerchug
Re: Crankshaft shimming [Re: CarpeDiem] #791548 11/28/19 4:41 pm
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Thermal conductivity of 360 aluminum is 150 W/(m K) and 5% chrome steel is 40 W/(m K).
https://www.engineeringtoolbox.com/thermal-conductivity-metals-d_858.html
Putting the case in a heated oven (bake, not broil, so it is the air doing the heating) the aluminum has a greater surface area than the bearing race so presumably the heat will conduct through the aluminum faster than the steel and expand at a faster rate than just the difference in linear expansion coefficient. It might be an interesting experiment with an IR camera to see the difference in temperature of the bearing and case in the oven. Possibly use a temperature crayon.
Allen, could it be the whipping of the crank is causing the ends of the rollers to dig into the race and flair the race? Needle bearings do not take shaft misalignment well.
The cam bush problem is unclear. It is now 0.878", standard is 0.874" and you have to ream it out further?

Re: Crankshaft shimming [Re: CarpeDiem] #791549 11/28/19 5:23 pm
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The even more whipping prone Norton twin crank works better with 20 to 25 end float, as the mains journal get to high revs they get wider on one edge so you need the space for this. The 'superblend' marketing term Norton came up with was just the normal roller bearing industry incremental design change of added crown on the edge of the rollers so they did not dig in, not a spherical roller. Now the question is did they add extra crown to needle rollers, I doubt they did so a shorter needle roller will have an easier life with a whippy crank. Be worth asking the needle roller makers if they do a extra crown on the needle bearing version in the A65 size.

Re: Crankshaft shimming [Re: CarpeDiem] #791558 11/28/19 7:58 pm
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Dave, the reference to the oven is how I normally get bearings or bushes out of a case, the bearings normally just drop out with no assistance.

You could be right on the needle roller, although the edge of the needle roller showed signs of crushing, it looked to have over heated in one spot and had cracked around the edge. I won’t rule out cracking but the bearing with the original crank didn’t have this and the different needle roller that I use now and sits further into the case hasn’t caused a problem either. The difference in the crank was when Devimead did the original crank they machines off the .020” step/thrust face from the crank web. The new crank didn’t get this despite the engineer having the original as a pattern. It’s worth adding also that the original crank in the same cases with the same bearing type had a lot more than 0.020” end float. I think the 1st and 3rd picture shows the bearing damage. The new bearing being sunk into the case further probably gives more room for whipping at the cheek end of the crank.

The mega cycle cam measured .004” over side on the timing side of the case only when compared to 3 other cams and to the drive side end. I needed to run a reamer through the timing side bushes until I had sufficient clearance.


beerchug
Re: Crankshaft shimming [Re: Allan Gill] #791565 11/28/19 10:20 pm
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Originally Posted by Allan Gill
the reference to the oven is how I normally get bearings or bushes out of a case, the bearings normally just drop out with no assistance.
Allan, I've seen a quite reasonable argument that it is better to start with a cold oven to avoid the risk of distorting fine features of the aluminium alloy part, so I've taken to using that approach. The article was in reference to die cast Japanese engines, which do have much finer casting features than our BSAs, so I can also appreciate the merits of your pre-heated oven approach.

It does take much longer, and possibly a slightly higher temperature, for the bearing to drop out with the initially cold oven, so I may well go back to pre-heating.

Re: Crankshaft shimming [Re: CarpeDiem] #791569 11/28/19 11:46 pm
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Before i rant on,,,, i have the greatest respect for Kommando's knowledge regarding bearings and mechanical engineering.
He's forgotten more than i'll ever know on the subject. I also wish to state that i am not intentionally
out to offend or upset anyone, my approach apparently tends to do this.

Compared to the norton crank, the a65 unit has nowhere near as much flex.
If you look at the journal diameters and 74 mm stroke plus it's one piece forged construction it's evident.
There are hundreds (maybe thousands) of needle roller converted a65 a70 variations around.
There are even more standard bushed motors around too.
I've put together some pretty rough end fed ones and never seen that problem before.
Indeed i've built some rough ones myself and raced them with some success.
I've also run a norton 360 deg crank in an a65 with needle timing side as well as 76 and 68 and 180 versions.

I doubt very much that whipping or flexing of the crank caused that problem on Alans motor.
It would have shown up when i used a 360 norton crank far more so than on Alan's standard a65 one.

I've just looked up the bsa specified end float it's 1.5-3 thou.
That means at running temp of say 90 degs? it will be at least 5 thou probably a fair bit more.

For that bearing to have chewed into the crank like that i'd be looking for something more than
a thou or so extra endfloat. The main bore alignment and individual bearing bores as to parallel
would be first.
Just my 2c.

Re: Crankshaft shimming [Re: CarpeDiem] #791570 11/29/19 12:20 am
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That bearing looks like it failed because of excess preload, caused by the 20 thou step on the crank.


71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: Crankshaft shimming [Re: gavin eisler] #791587 11/29/19 4:35 am
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Originally Posted by gavin eisler
That bearing looks like it failed because of excess preload, caused by the 20 thou step on the crank.


Yes i see that but surely he would have noticed when assembling that the crank was tight or no clearance at all.
The one hot spot indicates misalignment or even a slightly bent crank. Even so it must have been very tight to turn on assembly.
Surprising it didn't push the needle race through the timing side casting as there is only a thin lip there when machined for a needle race.

Re: Crankshaft shimming [Re: CarpeDiem] #791591 11/29/19 7:32 am
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I have to admit Nick that when I first got the motor back from the machine shop (crank fitted but not rods etc) the motor would spin fine with the outrigger on but was stiff to turn without the out rigger. After having the work done at a place where their work is usually of a very high standard I never gave it another thought. On hind sight I would have taken it back and said to machine the crank as per the original, but I carried on building surrendering to someone with more knowledge on engineering. Obviously tightening the outrigger nut was pulling the case somewhat allowing for more clearance. Which is why the crank could spin....

But would that then pull back when the case is up to temperature or has the crank grown?


beerchug
Re: Crankshaft shimming [Re: CarpeDiem] #791592 11/29/19 8:37 am
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NickL Offline
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In my experience the hot end float is always greater, i've measured it a few times.
Post mortems like this are always difficult especially when being done with no 'body'.


I remember Alex saying he had a similar thing on his bike where the drive side bearing
pushed out through the case. This has happened on one bike i worked on but it was due
to timing side thrust washer coming adrift and wedging down in between the crank and case,
that pushed the drive side bearing out. I suspect that was due to too much end float allowing
the washer to come adrift, but that motor was built so badly it's hard to say.

Re: Crankshaft shimming [Re: NickL] #791595 11/29/19 11:31 am
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kommando Online Content
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Originally Posted by NickL
Before i rant on,,,, i have the greatest respect for Kommando's knowledge regarding bearings and mechanical engineering.
He's forgotten more than i'll ever know on the subject. I also wish to state that i am not intentionally
out to offend or upset anyone, my approach apparently tends to do this.


No offence taken wink , just throwing out a grain of sand in case it draws out a potential solution. Too much knowledge can sometimes limit your thoughts from personal experience. Will continue to add the odd grain now and again.

Re: Crankshaft shimming [Re: CarpeDiem] #791600 11/29/19 1:07 pm
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Mark Parker Offline
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Joining the conversation; I originally used a combination bearing on both A10 crank and Norton crank in my motor, with the Norton crank the combination bearing would move, I had countersunk screws trying to hold that bearing and it wouldn't stay put. To try to fix it meant splitting the cases, why I went to a straight heavy series Nkis 30 roller and used the outrigger bearing to control end float and crank position. If it stuffed up it was just under the primary cover and easy to get at, no more splitting cases.

It masks the timing marks so before fitting the head I set the engine at where I want a cyl to fire and drill through a hole in the bearing mount into the alternator and mark both cyl positions for strobing doing one big and one little can differentiate between left and right cyls or putting red paint in one hole if they are drilled the same.

The NKIS 30 I first fitted was std clearance a little crush of the case and it was a bit tight fitting, years later I had it apart and checked main bearings, The Norton Drive side roller had excess up and down play, the needle roller was still a bit tight. So I replaced both, the needle roller this time in C3 clearance to account for the slight crush. That type of needle roller has never moved in the case, and I expect because it's not the bearing taking side thrust. While the outrigger bearing is fully captured and cannot move.

I've seen another type of roller conversion stuff up because the L/ends were pushed out of the rods because the crank was so far to one side and the rods were pushing hard against the piston bosses.


mark
Re: Crankshaft shimming [Re: CarpeDiem] #791655 11/29/19 11:37 pm
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NickL Offline
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I rather liked these https://www.skf.com/uk/products/rol...edle-roller-bearings/productid-NKXR%2035

Didn't use the radial roller, made a bronze thrust washer. So limiting speed was NA. Available in c3.
We used to cut a small notch in the flange and pin it for anti rotation.
Did the job very well but an expensive bearing.

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